The Humphrey Company started in the early 1900's, as the General Gas Light Company in Kalamazoo, Michigan. In 1916, they patented the Radiantfire gas heater (there are many different models), which operated on natural gas, heating a set of ceramic inserts that would glow and radiate heat into the room. They became very popular and sold well. By 1920 there were over 700,000 already installed and the company was turning them out at rates up to 150,000 a year. Because of that, there are enough still around to keep prices pretty reasonable. The highest one sold for recently on Ebay was about $255 in excellent working order, others sold for as little as $15-$20.